Add basic Ceilometer alarm test

This sends a manual ceilometer sample to trigger the alarm,
then confirms that the autoscale policy/group reacts correctly.

Note: this doesn't used ScenarioBaseTest as it skips the test
unnecessarily on unused images and networks.

Change-Id: I5c842779d90497ba88df66bbfd8f447679645192
Depends-On: Ib3795bcca9d5ec3d68c6443a9854dbc56118ca40
diff --git a/common/test.py b/common/test.py
index 7c8300d..4168fb4 100644
--- a/common/test.py
+++ b/common/test.py
@@ -87,6 +87,7 @@
         self.network_client = self.manager.network_client
         self.volume_client = self.manager.volume_client
         self.object_client = self.manager.object_client
+        self.metering_client = self.manager.metering_client
         self.useFixture(fixtures.FakeLogger(format=_LOG_FORMAT))
         self.updated_time = {}